Antibody Therapy
Antibody therapy has been established for the targeted treatment of subjects with cancer, immunological and angiogenic disorders (Carter, P. (2006) Nature Reviews Immunology 6:343-357). The use of antibody-drug conjugates (ADC), i.e. immunoconjugates, for the local delivery of cytotoxic or cytostatic agents, i.e. drugs to kill or inhibit tumour cells in the treatment of cancer, targets delivery of the drug moiety to tumours, and intracellular accumulation therein, whereas systemic administration of these unconjugated drug agents may result in unacceptable levels of toxicity to normal cells (Xie et al (2006) Expert. Opin. Biol. Ther. 6(3):281-291; Kovtun et al (2006) Cancer Res. 66(6):3214-3121; Law et al (2006) Cancer Res. 66(4):2328-2337; Wu et al (2005) Nature Biotech. 23(9):1137-1145; Lambert J. (2005) Current Opin. in Pharmacol. 5:543-549; Hamann P. (2005) Expert Opin. Ther. Patents 15(9):1087-1103; Payne, G. (2003) Cancer Cell 3:207-212; Trail et al (2003) Cancer Immunol. Immunother. 52:328-337; Syrigos and Epenetos (1999) Anticancer Research 19:605-614).
Axl
Axl is a member of the receptor tyrosine kinase sub-family. Although similar to other receptor tyrosine kinases, the Axl protein represents a unique structure of the extracellular region that juxtaposes IgL and FNIII repeats, and has an intracellular region containing an intracellular domain, part of which is the kinase domain. Axl transduces signals from the extracellular matrix into the cytoplasm by binding growth factors like vitamin K-dependent protein growth-arrest-specific gene 6 (Gas6). The extracellular domain of Axl can be cleaved and a soluble extracellular domain of 65 kDa can be released. Cleavage enhances receptor turnover and generates a partially activated kinase (O'Bryan J P, etal (1995) J Bioi Chern. 270 (2): 551-557).
Structural information relating to the human Axl gene and gene product is described in WO2003/068983. The following patent publications also relate to Axl or other tyrosine kinase receptors: U.S. Pat. Nos. 5,468,634; 6,087,144; 5,538,861; 5,968,508; 6,211,142; 6,235,769; WO1999/49894; WO2000/76309; WO2001/16181 and WO2001/32926.
Axl is involved in the stimulation of cell proliferation. Specifically, Axl is a chronic myelogenous leukaemia-associated oncogene, that is also associated with colon cancer and melanoma. It is in close vicinity to the bcl3 oncogene which is at 19q13.1-q13.2. The Axl gene is evolutionarily conserved among vertebrate species, and is expressed during development in the mesenchyme.
Upon interaction with the Gas6 ligand, Axl becomes autophosphorylated, and a cascade of signal transduction events takes place. PI3K, AKT, src, Bad, 14-3-3, PLC, ERK, S6K (mitogen-regulated kinase) and STAT are each known to be involved in this cascade. Gas6 has a region rich with y-carboxyglutamic acid (GLA domain) that allows for Ca++-dependent binding to membrane phospholipids. Gas6 is a weak mitogen and has an anti-apoptotic effect in NIH3T3 fibroblasts subjected to stress by TNF-induced cytotoxicity, or growth factor withdrawal. In NIH3T3 the binding of Gas6 to Axl results in activation of PI3K, AKT, src and Bad.
Studies have shown that Axl plays a number of different roles in tumour formation. Axl is a key regulator of angiogenic behaviours including endothelial cell migration, proliferation and tube formation. Axl is also required for human breast carcinoma cells to form a tumour in vivo, indicating that Axl regulates processes that are vital for both neovascularisation and tumorigenesis (Holland S. et al, Cancer Res 2005; 65 (20), Oct. 15, 2005).
The activity of Axl receptor tyrosine kinase is positively correlated with tumour metastasis. More specifically, studies have shown that Axl enhances expression of MMP-9, which is required for Axl-mediated invasion. Axl promotes cell invasion by inducing MMP-9 activity through activation of NF-BK and Brg-1 (Tai, K-Y et al, Oncogene (2008), 27, 4044-4055). Axl is overexpressed in human glioma cells and can be used to predict poor prognosis in patients with Glioblastoma Multiforme (GBM) (Vajkoczy P. et al, PNAS, Apr. 11, 2006, val 103, no. 15, 5799-5804; Hutterer M. etal, Clinical Cancer Res 2008; 14 (1) Jan. 1, 2008). Axl is also relatively overexpressed in highly invasive lung cancer cell lines compared to their minimally invasive counterparts (Shieh, Y-S etal, Neoplasia, val 7, no. 12, December 2005, 1058-1064). Axl is therefore believed to play an important role in tumour invasion and progression.
Likewise, Axl is expressed in highly invasive breast cancer cells, but not in breast cancer cells of low invasivity. More specifically, inhibition of Axl signalling (by dominant-negative Axl mutant, an antibody against the extracellular domain of Axl, or by short hairpin RNA knockdown of Axl) decreased the mobility and invasivity of highly invasive breast cancer cells. Small molecule Axl inhibitors interfered with motility and invasivity of breast cancer cells. Thus, Axl is understood to be a critical element in the signalling network that governs the motility/invasivity of breast cancer cells (Zhang, Y-X et al., Cancer Res 2008; 68 (6), Mar. 15, 2008).
In mesangial cells, Gas6 was found to have a mitogenic effect, indicative of a possible role in the progression of glomerulosclerosis. Evidence has suggested that the Gas6/Axl pathway also plays a role in glomerulonephritis (Yanagita M. at al, The Journal of Clinical Investigation; 2002, 110 (2) 239-246). Further studies have shown that Gas6 promotes the survival of endothelial cells in a model for arterial injury. Angiotensin II, via its AT1 receptor, was shown to increase Axl mRNA and protein receptor in vascular smooth muscle cells (Melaragno M. G. etal, Circ Res., 1998, 83 (7): 697-704). Axl has also been shown to be involved in cellular adhesion, cell proliferation and regulation of homeostasis in the immune system (Lu Q., 2001) Science 293 (5528): 306 311). Following Axl activation, the following phenomena have been observed: inhibition of apoptosis, increase in “normal” cell (non-transformed) survival of fibroblasts and endothelial cells, migration of Vascular Smooth Muscle Cell (VSMC) (inactivation of the Axl kinase blocks migration), enhancement of neointima formation in blood vessel wall (Melaragno M. G. etal, Trends Cardiovasc Med., 1999, (Review) 9 (8): 250-253) and involvement in lesion formation and the progression of atherosclerosis.
Therapeutic uses of anti-AXL ADCs
The efficacy of an Antibody Drug Conjugate comprising an anti-AXL antibody (an anti-AXL-ADC) in the treatment of, for example, cancer has been established—see, for example, WO2016/166297, WO2016/166302, GB1702029.8, GB1719906.8, and PCT/EP2018/053163.
Research continues to further improve the efficacy, tolerability, and clinical utility of anti-AXL ADCs. To this end, the present authors have identified clinically advantageous combination therapies in which an anti-AXL ADC is administered in combination with at least one secondary agent.